In this project, we are attempting to study cell surface antigens which are specific to tumors. For this purpose, we are producing hybridomas from mice which have been immunized with human leukemia and lymphoma cells. The objective is to find antibodies which are useful in categorizing and diagnosing human lymphoid malignancies. Techniques of flow cytometry of cells in suspension and immunoperoxidase of frozen tissue sections are being employed. A number of monoclonal antibodies are being made available for clinical application.